linux-kernel - Re: Scheduler broken? sdhci issues with scheduling

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Message-ID: <20080229133433.GA15532@elte.hu>
Date:	Fri, 29 Feb 2008 14:34:33 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	huggie@...th.li, linux-kernel@...r.kernel.org
Cc:	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: Scheduler broken? sdhci issues with scheduling

* Simon Huggins <huggie@...th.li> wrote:

> [ Please Cc me on replies ]
> 
> I had a bug with sdhci which Pierre Ossman looked at for me.
> 
> In the end essentially the fix was to use HZ=1000 and nothing else. 
> Pierre seemed to think that this was a bug in the scheduler.

does the patch below help, even if you keep HZ=100? This doesnt look 
like a scheduler issue, it's more of a timer/timing issue. Different HZ 
means different msleep() results - and the mmc code does a loop of small 
msleep delays.

	Ingo

-------------->
---
 drivers/mmc/core/core.h |    7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

Index: linux/drivers/mmc/core/core.h
===================================================================
--- linux.orig/drivers/mmc/core/core.h
+++ linux/drivers/mmc/core/core.h
@@ -36,12 +36,7 @@ void mmc_set_timing(struct mmc_host *hos

 static inline void mmc_delay(unsigned int ms)
 {
-	if (ms < 1000 / HZ) {
-		cond_resched();
-		mdelay(ms);
-	} else {
-		msleep(ms);
-	}
+	mdelay(ms);
 }

 void mmc_rescan(struct work_struct *work);
--
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